The invention relates to water-based hardwood floor finishing products and methods of applying the products on site.
Hardwood flooring has long enjoyed favor with consumers due to the unique richness and elegance that it adds to a home or business setting. Although hardwood flooring is a consumer favorite, inherent physical characteristics of hardwood flooring make it susceptible to damage from ordinary usage and the occasional accident. As such, it has become traditional practice in the flooring industry to protect hardwood floors with some form of coating or finish to preserve aesthetic qualities, and ultimately extend the useful life of the surface.
Many protective finishes are known in the flooring industry. Protective finishes in the prior art include varnishes, acrylics, urethanes, and epoxies or combinations thereof. In general, protective finishes are applied to hardwood surfaces in successive layers, with each layer performing a specific purpose. For example, a protective finish normally constitutes primers applied directly to the hardwood surface to bond and seal the porous wood itself and top coat layers applied over the sealing layers to provide sheen and stain resistance. In recent years, water-based finishes (i.e., solutions in which water is the primary solvent) have become popular due to environmental and health concerns. In addition, various layers may also contain additives including co-solvents, defoamers, flow additives and wax emulsions to provide ease of application and improve the overall effectiveness of the protective finish.
Although the above-mentioned primers and top coats provide some protection against mechanical damage due to scratching, gouging, scuffing or the like, the hardwood flooring industry has invested much time and effort into identifying further additives for floor finishes in order to improve the overall durability of hardwood floor surfaces. Unfortunately, increasing finish durability often results in a finish with reduced abilities to preserve aesthetic qualities. Thus, the fine balance between durability and preservation of desirable characteristics such as clarity is difficult to attain. Nonetheless, such finishes are extremely desirable.
Finished hardwood floors also suffer from a problem termed panelization. Panelization, to be more thoroughly discussed below, results when resins contained in the primer coat invade the gaps between hardwood boards, cross-link, and cause neighboring boards to become rigidly affixed to each other as if glued together. Unfortunately, when hardwood boards contract due to seasonal changes in humidity, large sections of panelized flooring contract to leave unsightly, uneven gaps at the boundaries of the panelized units. Without panelization, the gaps between boards would be evenly distributed, and hence smaller and less noticeable throughout seasonal humidity cycles. A method of finishing hardwood floors that avoids this problem, but provides durability and is aesthetically pleasing, is needed.
The invention is a hardwood floor finishing method that uses water-based coatings and exhibits improved durability during ordinary usage and against accidental damage. It also substantially reduces or eliminates the above mentioned panelization problem. In general, the finishing method is intended to be carried out on-site in several simple, efficient and safe steps. In its preferred form, the method involves the application of a ceramic-based armor coat over the primer layers in order to improve the durability and wearability of the floor finish.
The inventive method disclosed herein is preferably implemented on a new floor by applying successive layers of primer, ceramic armor and top coat to a newly screened, cleaned and tacked hardwood surface. The primer is a water-based primer having a low solid content and low co-solvent concentration in order to reduce or eliminate panelization. As with many conventional primers, the primer contains a mixture of acrylic and polyurethane polymer resin dispersions that are not water-soluble, but are suspended in the water/co-solvent mixture. Alternatively, the primer may be a copolymer substitute for the acrylic and polyurethane mixture. Upon application to the prepared surface, this water-based primer penetrates the pores of the hardwood and acts to thoroughly seal the exposed hardwood surface. Use of a water-based primer to seal a hardwood surface is widely known in the field. However, as mentioned, the method disclosed herein involves applying a water-based primer having an unusually low resin content and low co-solvent concentration. It is believed that the combination of the low resin content and a low co-solvent concentration reduces the flow of resins into the gaps between the hardwood boards during the initial drying process. A second coating of primer is applied after initial drying of the first primer coat. Two coats of primer are needed because the coats are thin. The problem posed by panelization of hardwood floor boards is substantially eliminated by using a thin coating of low solid content/low co-solvent concentration primer, but a sufficient primer build is obtained by using two coats of primer.
It has been found that panelization results from the use of primers having a high solid content of polymers or copolymer resins and a high concentration of co-solvent. This combination promotes not only the flow of uncrosslinked polymer or copolymer resins into the existing gap between new hardwood boards but also the subsequent solvation step necessary to cross link the resins. However, the polymer or copolymer resins remain uncrosslinked when in a solution having a high water content. Only when water is removed as by evaporation, are the polymer or copolymer resins solved into the increasing concentration of co-solvent. Once solved, the polymer or copolymer resin crosslink into a rigid composition potentially resulting in a group of boards being joined or glued together to form a panel-like unit. It should be noted that hardwood normally contracts in a direction across the grain, and therefore the width of the boards normally shrinks when the hardwood boards respond to seasonal changes in humidity. The unfortunate result of this phenomenon on a panelized floor is that gap width is consequently spread unevenly across the floor surface. Instead of small gaps of uniform width existing between each new hardwood board, a panelized group of boards will have essentially no gaps on its interior, but much larger and noticeable gaps will surround the panel. The gaps due to panelization are especially evident during the winter when humidity is relatively low. These noticeable gaps in the hardwood surface are obviously undesirable.
The low concentration of acrylic and polyurethane polymer resins or copolymer resins in the primer effectively reduces the concentration of uncrosslinked resin in the gap area when the primer is first applied. Subsequently, the concentration of the crosslinked resins in the gap area remains relatively low for an extended time period because the water within the gaps takes longer to evaporate than on the hardwood boards"" exposed surfaces. Thus, if a second layer of primer is applied within a certain amount of time (e.g. about 45 minutes), the gap area between hardwood boards remains relatively free of cured resins.
After the primer layers are dry, the floor is then screened, vacuumed and tacked with a dampened cloth to remove all dust particles. Then, within about two to three hours of applying the second primer coat, the armor coat is applied to the floor. The armor coat effectively seals over the gap which should at this time still contains the primer solution with a relatively high concentration of water. The primer solution in the gap area is consequently left undried. In this manner, the resins in the armor coat are not allowed to reside deep within the gaps. Rather, as the armor coating dries, it forms a relatively thin bridge across the gap between the boards. Within twenty-four hours, the top coat should be applied over the armor coat. When the top coat and the armor coat continue to dry and cure over time, the coats shrink and the thin bridging across the gaps cracks easily. Also, the high content of water contained within the sealed off gap area is slowly absorbed into the porous walls of the neighboring hardwood boards. Left behind is a small amount of crosslinked resin which does not act as glue between hardwood boards. The gap area will ultimately be completely open and each hardwood board may expand and contract independently of their neighbor. In sum, individual hardwood boards do not become rigidly attached to each other and the unsightly effects of panelization are greatly reduced or eliminated totally.
The preceding paragraphs discuss the method for finishing newly constructed hardwood floors. However, when finishing older hardwood floors, panelization, if it is going to occur, will have probably already occurred. Thus, there is no advantage in applying a primer layer with panelization-inhibiting abilities to older hardwood floors that have previously been finished. Thus, the preferred method of finishing an older hardwood surface involves buffing the old finish and applying the armor coat and top coat directly on the buffed surface. Alternatively, the existing finish can be removed by sanding and a traditional high solid content primer can be applied in order to provide a sufficient build on the surface. High solid content primers, as noted previously, are widely known in the field.
In addition to offering a remedy for panelization problems, the preferred embodiment of the invention also provides an approach to improving the durability of the hardwood floor coating. The use of ceramic additives (e.g. aluminum oxide) to provide abrasion resistance and durability in floor finishes has been widely discussed in the prior art. Normally, the aluminum oxide particles are relatively small and embedded into the cured resin. In the preferred embodiment of the invention, however, relatively large-sized ceramic particles are mixed into the water-based armor coat. Also, the armor coat has a low resin content. This provides the fully cured finish with a unique microscopic bead structure on its surface. Standard abrasion resistance testing has shown that the microscopic bead structure provides a finished hardwood floor with extremely high durability.
More specifically, the diameter of the large particles of ceramic additive (e.g., aluminum oxide) are preferably in the range of 15 to 35 microns. When the armor coat is applied over the panelization-reducing primer layer(s), a large percentage of the non-ceramic components (i.e. water and co-solvent) in-the armor coat evaporate completely. The components left behind, namely the crosslinked acrylic and polyurethane polymers (or copolymers), produce a thin layer of hardened resin in which the larger ceramic particles remain protruding above. These protrusions are termed microbeads. The microbeads on the surface of top coat layer remain even after subsequent applications of a water-based top coat layer over the heterogeneous armor coat layer. An incidental benefit of the microbeaded top coat surface is the anti-slip characteristics bestowed on the surface due to the increased frictional coefficient of the microbeaded top coat layer.
It should be apparent to those skilled in the art that the invention provides a practical and simple hardwood floor finishing method that yields a finish resistant to the problems of panelization. In another aspect, it should also be apparent that the finish is convenient to apply on-site and also provides exceptional durability. The finishing method is easy to apply on-site to both newly constructed hardwood floors and old hardwood floors in need of refinishing. In addition, the invention provides an environmentally safe method that generates no noxious fumes and contains no caustic agents. It is safe for both the people that work with the system and the environment in general.